Mixtures and Solutions Test Review

​Mixtures and Solutions Test Review

​Truths about Models

• Models are used to communicate information

• Models are used to test a system

• Model are communicated through words and drawings

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​Untruths about Models

• Models must be smaller than the objects they represent

• Models once designed, stay the same over time

• Models must be built to look exactly like the real thing in every detail

​Models in Science

​Mass

• Mass is how much something weighs

• When you combine two or more substances, their mass will be their combined total.

• Example:

  If you combine sugar that weighs 20 grams with water that has a volume of 30 milliliters. (30 milliliters is equivalent to 30 grams)

  The total weight of the sugar water will be 20 + 30 = 50 grams.

​A fifth-grade student was showing his grandma what he was learning in science class. He mixed 30 grams (g) of a white powder in 90 milliliters (mL) of warm water. The water stayed clear. ​

a. Draw and label a model to show what happened to the white powder when it mixed with the warm water.

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b. How do you find the weight of the solution? What is the weight?

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Multiple Choice

What is the total mass when you combine 30 grams of salt to 60 milliliters of water?

• 30 grams

• 60 grams

• you can't combine grams and milliliters

• 90 grams

Multiple Choice

What is the combined mass of 25 grams of a white powder and 50 milliliters of water?

• 25 grams

• 75 grams

• 50 grams

• I don't know how to solve this

Density

​Density is how much mass there is in a particular space.

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​Imagine a drawer full of socks. If you take out a pair of socks, the density of the drawer is going to change. This is because the mass of the socks has changed but the volume of the drawer has stayed the same.

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Density = Volume ÷​ Mass

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When you compare density of two ​items (if volume is the same) the heavier one has the greater density.

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​Look at the data in the table below. The volumes are all the same so you would look at the mass to determine which substance was the most dense. The more the substance weighs the more dense that substance is.

Multiple Choice

Put the substances in order from the least dense to the most dense.

• G, B, H, W

• W, H, B, G

• B, W, H , G

• G, H, W, B

Multiple Choice

Which item is the most dense (all volumes are the same)

corn syrup 65 miligrams

water 42 milligrams

rubbing alcohol 36 miligrams

• the corn syrup

• the water

• the rubbing alcohol

• the all have the same density

Multiple Choice

Which item is the least dense (all volumes are the same)

salt water 2 grams

sugar water 3 grams

koolaid 3.5 grams

• the salt water

• the sugar water

• the koolaid

• all the densities are the same

​Separating Mixtures

​Think back to the experiment we did....

If you had a container that was filled with salt water, pebbles, sand, and silt.  Describe a method that would separate all the different particles and explain why that method would work.​ Use a model to explain your method.

​Solutions

• When you combine 2 or more substances and one or more of them dissolves into the solvent

• Examples:

  salt and water

  sugar and water

  kool-aid

• All particles are still present

• No new substance is formed. You still have the solute and the solvent. The solute has just dissolved into the solvent.

Multiple Choice

You are making limeade. You mix the lime juice, water, and sugar together. Have you created a new substance? Explain how you know.

• Yes, this is a new substance. I created limeade

• No, this is just a solution. The lime juice and sugar just dissolved in the water.

• Yes, this is a new substance. There was a chemical reaction when you mixed the lime juice and water.

• I don't understand this question.

​States of Matter

• Solid

  molecules are tightly packed, very dense, volume consistent (doesn't take on shape of container)

• Liquid

  molecules are less packed but still attracted to each other, takes on shape of container

• Gas

  molecules are far apart, no definite shape or volume, low density,

Multiple Choice

What is the term that describes when a substance moves from the solid state of matter to the liquid state of matter?

• Evaporating

• Condensing

• Freezing

• Melting

Multiple Choice

What is the term that describes when a substance moves from the gas state of matter to the liquid state of matter?

• Evaporating

• Condensing

• Freezing

• Melting

Multiple Choice

What is the term that describes when a substance moves from the liquid state of matter to the gas state of matter?

• Evaporating

• Condensing

• Freezing

• Melting

Multiple Choice

What is the term that describes when a substance moves from the liquid state of matter to the solid state of matter?

• Evaporating

• Condensing

• Freezing

• Melting

​Chemical Reactions and Molecules

​In a chemical reactions, the molecules from the substances rearrange to form new substances. All chemicals are still present but are combined differently.

In the example above: 1 methane molecule and 2 oxygen molecules are combined to form 1 carbon dioxide molecule and 2 water molecules.

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You still have hydrogen, carbon, and oxygen from the original substances but they are combined differently after the reaction. ​

Multiple Choice

The farmer left his 2 identical rakes outside for several weeks. One rake rusted and the other rake didn't. Why do you think this happened?

• one rack was plastic and the other rake was metal

• The farmer only used 1 of the rakes

• One of the rakes got wet so it rusted. The other one didn't get wet so it didn't rust.

• The farmer shouldn't leave his rakes outside.

Multiple Choice

I had a glass of ice water. The ice melted. After the ice melted will the glass of water weigh more or less than before? Why?

• It will weigh less because the ice melted so there is less matter.

• It will weigh more. The ice weighs less than the liquid water in the glass.

• It will weigh the same. The ice just changed state but weighs the same.

• I don't understand this question.