REVIEWER IN SCIENCE VI

Risha designs an experiment with two pans of soil: one with grasses and one without. The pans will be tilted, and water will be sprinkled over them. What is the best hypothesis for Risha’s experiment?

• If soil has no plants, then the water will become muddy when it flows.

• If grasses are present in the soil, then the water will remain clearer.

• Loose soil without plants causes more erosion when water runs over it.

• If soil has plants, then erosion will be reduced compared to soil without plants.

Answer explanation

The hypothesis "If soil has plants, then erosion will be reduced compared to soil without plants" directly addresses the impact of grasses on soil erosion, making it the best choice for Risha's experiment.

Your Science teacher told you to bring materials for your experiment. There are three different but common liquids found at home and school that can be used in the activity. Liquid A is water, liquid B is vinegar and liquid C is cooking oil. Which liquids will likely dissolve each other? Which liquid will not dissolve each other?

• Water and vinegar will dissolve each other; cooking oil will dissolve with vinegar.

• Water, vinegar and cooking oil will dissolve each other.

• Water and cooking oil will dissolve each other. Vinegar and cooking oil will not dissolve each other.

• Vinegar and water will dissolve each other; cooking oil will not dissolve either in vinegar or water.

Answer explanation

Vinegar and water are both polar substances, allowing them to mix and dissolve in each other. Cooking oil, being non-polar, does not dissolve in either vinegar or water, making the correct choice clear.

What is the difference between a suspension and a colloid?

• Suspensions are medicines while colloids are for food.

• Suspensions may appear cloudy while colloids are muddy.

• Suspensions lose their consistency while colloids remain consistent

• Suspensions are not uniformly distributed in solvents while colloids are uniformly distributed.

Answer explanation

The correct choice highlights that suspensions are not uniformly distributed in solvents, meaning their particles can settle over time, while colloids have particles that remain evenly distributed, giving them a stable appearance.

Teacher Becky discussed winnowing as a method of separating mixtures. Based on her discussion, which of the following CORRECTLY describes the technique of separating mixtures called winnowing?

• It is a process of separating mixtures by allowing solid chaff is mixed to be mixed with water and settle at the top.

• It is a process of separating the mixture by handpicking the rice grains from the rice chaff

• It is the process of freeing grain from the lighter particles of chaff by throwing it into the air and allowing the wind forced current of air to blow away impurities.

• It is when the rice chaff is allowed to settle at the bottom of the container and then it will be scooped to separate the chaff.

Answer explanation

Winnowing is correctly described as the process of throwing grain into the air, allowing the wind to blow away lighter chaff, thus separating impurities from the grain.

You are experimenting to see if the type of soil affects plant growth. What would be the independent variable?

• amount of water given

• height of the plants

• type of soil used

• amount of sunlight

Answer explanation

The independent variable is the factor you change in an experiment. In this case, the type of soil used is what you are testing to see its effect on plant growth, making it the independent variable.

What is the main purpose of having a control group in an experiment?

• to serve as a comparison

• to test the hypothesis

• to collect data

• to formulate a new question

Answer explanation

The main purpose of having a control group in an experiment is to serve as a comparison. It allows researchers to determine the effect of the independent variable by comparing results against the control group, which does not receive the treatment.

Which of the following substances is an example of a compound?

• Aluminum

• Sugar

• Sulfur

• Gold

Answer explanation

Sugar is a compound made of carbon, hydrogen, and oxygen atoms, while aluminum, sulfur, and gold are elements. Therefore, sugar is the correct example of a compound.

Which of the following substances is an example of a compound?

• Aluminum

• Sugar

• Sulfur

• Gold

Answer explanation

Sugar is a compound made of carbon, hydrogen, and oxygen atoms, while aluminum, sulfur, and gold are elements. Compounds consist of two or more different elements chemically bonded together, making sugar the correct choice.

What kind of mixture is sinigang? Why?

• Sinigang is a homogeneous mixture since it has lots of ingredients.

• Sinigang is a homogeneous mixture since it has lots of ingredients dissolved in its tamarind based.

• Sinigang is a heterogeneous mixture since it has different distinguishable ingredients of vegetables, meat and other spices.

• Sinigang is a heterogeneous mixture since it has a palatable taste.

Answer explanation

Sinigang is a heterogeneous mixture because it contains various distinguishable ingredients like vegetables, meat, and spices, which can be seen and separated, unlike a homogeneous mixture where components are uniformly distributed.

Why do colloids not separate into distinct layers despite their classification as heterogeneous mixtures?

• Colloidal particles are too small to coalesce and separate from the solvent.

• Colloidal particles are too large to be effectively dissolved in the solvent.

• Colloidal particles have medium solubility in the solvent.

• Colloidal particles have high solubility in the solvent.

Answer explanation

Colloidal particles are too small to coalesce and separate from the solvent, which prevents them from settling into distinct layers, maintaining their stable dispersion in the mixture.