Sec 1 Science Elements, Compounds & Mixtures topical questions

Classify each substance as an element, a compound or a mixture.

1. (a)Oxygen[1]
2. (b)Carbon dioxide[1]
3. (c)Air[1]

In a cup of sweet tea, name the solute and the solvent. State what the sweet tea is called once the sugar has dissolved.

State two differences between a compound and a mixture.

State two ways to make salt dissolve faster in water.

Give one example of a metal and one example of a non-metal.

A student mixes iron filings with yellow sulfur powder. She can still see both, and a magnet picks up the iron.

1. (a)Is this product an element, a compound or a mixture? Explain.[2]
2. (b)She then heats the mixture strongly and a new black solid forms. The magnet no longer picks out iron. What has the black solid become?[1]
3. (c)State one way the properties of the black solid differ from the properties of the mixture.[1]

Compare a salt solution with a suspension of chalk in water.

1. (a)State one way they look different after being left to stand.[1]
2. (b)Which one can be separated by filtration? Explain.[2]
3. (c)Name the solute and the solvent in the salt solution.[1]

A student investigates how temperature affects the time for a vitamin tablet to dissolve.

1. (a)Name the independent variable and the dependent variable.[2]
2. (b)State two variables she must keep the same.[2]

Explain why sorting rubbish into metal, glass and plastic helps recycling.

Water is a compound of hydrogen and oxygen. Hydrogen burns and oxygen supports burning. Explain why these facts do not mean water is a fire risk in the same way.

A student says, “I crushed the sugar, so more sugar dissolved.” The beaker was already holding as much dissolved sugar as it could at that temperature, and some solid was still left. Evaluate the statement.

Four labels have fallen off: distilled water, muddy water, air, and a piece of copper. Describe one test or observation that identifies each.

Seawater is described as a mixture, and water is described as a compound. Explain both descriptions.

A factory recovers copper from a pile of mixed waste. Explain why knowing the chemical composition of the waste matters, and why a mixture of copper pieces and plastic is easier to separate than a compound that contains copper.

Two beakers contain seawater. Beaker A is stirred at 25 °C. Beaker B is not stirred, and it is at 25 °C as well. Both already look clear, with no solid left.

1. (a)Will further stirring make more salt dissolve in beaker A? Explain.[2]
2. (b)State one change that could let more salt dissolve.[1]